The present invention relates to networks that can accommodate a wide variety of mobile nodes (e.g. laptop computers). More specifically, the invention relates to address translation systems for mapping IP addresses of the mobile nodes to globally unique IP addresses available on a network where mobile nodes temporarily attach.
Private networks are commonly connected to the Internet through one or more routers so that hosts (PCs or other arbitrary network entities) on the private network can communicate with nodes on the Internet. Typically, the host will send packets to locations both within its private network and on the Internet. To receive packets from the Internet, a private network or a host on that network must have a globally unique 32-bit IP address (or, if necessary, a larger address as specified in IP version 6). Each such IP address has a four octet format. Typically, humans communicate IP addresses in a dotted decimal format, with each octet written as a decimal integer separated from other octets by decimal points.
Global IP addresses are issued to enterprises by a central authority known as the Internet Assigned Number Authority (“IANA”). The LANA issues such addresses in one of three commonly used classes. Class A IP addresses employ their first octet as a “netid” and their remaining three octets as a “hostid.” The netid identifies the enterprise network and the hostid identifies a particular host on that network. As three octets are available for specifying a host, an enterprise having class A addresses has 224 (nearly 17 million) addresses at its disposal for use with possible hosts. Thus, even the largest companies vastly under use available class A addresses. Not surprisingly, Class A addresses are issued to only very large entities. Class B addresses employ their first two octets to identify a network (netid) and their second two octets to identify a host (hostid). Thus, an enterprise having class B addresses can use those addresses on approximately 64,000 hosts. Finally, class C addresses employ their first three octets as a netid and their last octet as a hostid. Only 254 host addresses are available to enterprises having a single class C netid.
With increasing frequency people travel, for business and pleasure, with portable computers. Laptop computers have become ubiquitous in the work force. In an effort to become ever more productive, individuals travel with these tools so that they can work essentially anywhere. Often work requires that the individual access the Internet. Even if their work does not require this, many individuals wish to remain in communication with their colleagues via the Internet.
Many enterprises would like to accommodate this propensity by allowing all customers or visitors to use their own computers to access the Internet while they visit the enterprise. Examples of such enterprises include hotels, airport kiosks, hospitals, etc.
If a user desires to take a computer that is normally attached to a home network and travel with it so that it attaches to a different, remote, network, the node cannot automatically communicate over the remote network. First, the mobile node is usually configured to send messages through a specified router at its home network. Because it is no longer present at the home network and the specified router cannot be immediately located, communications from the mobile node will not be sent by the remote network. In addition, communications to the mobile node will be routed to the node's home network. Because the router there will not know where to forward the packet, the communications will be lost.
To allow remote connections, some mobile computers use Dynamic Host Configuration Protocol (DHCP), which is described in RFC 2131, incorporated herein by reference for all purposes. In this protocol, the computer is told to ask the network—according to prescribed rules—for a temporary network address. Thus, DHCP allows mobile nodes to connect to the Internet via remote networks. From the perspective of a hotel or other entity wishing to provide Internet access to all visitors, this is well and good so long as all visiting nodes are configured to work within the DHCP protocol. Unfortunately, this is not the case. Many computer users, who have traditionally been stationary users, have obtained mobile computers and now travel with these machines. Many such users are not even aware of DHCP. Thus, if a hotel is to rely on DHCP for the connectivity of its visitors, many of its visitors will not be able to easily connect.
There are alternative, more universally applicable, possibilities. If the visiting node has a statically configured IP address, that IP address can be adjusted. Conventional computer operating systems such as Windows 95®, Windows 98®, Windows NT®, Macintosh® OS, etc. have a setting in which the user can choose a new IP address or set the computer to dynamically take on an IP address assigned by the new network. Thus, a computer can have its IP address reset to be compatible with a remote network. The problem with this approach is that the cost of reconfiguring the IP address (it is not a trivial procedure) in a remote computer exceeds the advantage to the enterprise providing the remote network connection. Further, when the computer moves back to its home network (or to some other network), it must again have its IP address reset via the complicated procedure. Except in the rare case of an unusually sophisticated user, at least two adept persons other than the computer user must be involved in cycling the computer from its home IP address to a remote IP address and back again.
Alternatively, a remote network configured with a Network Address Translation (or “NAT”) could be reconfigured to accommodate the visiting node. However, this will require a highly sophisticated network administrator, in communication with the visitor at her computer, resetting the remote network's list of available “inside addresses” for address translation. This approach is even less cost effective than setting and resetting the static IP address of the visiting node.
FIG. 1A illustrates the general-purpose currently available approaches to network connectivity for a statically configured laptop or other mobile node. As illustrated, the Internet 101 allows nodes on a home network 103 to communicate with nodes on a remote network 105. In this specific example, a node 107 having a static IP address is normally connected to home network 103. In other words, network 103 is the home network for mobile node 107.
Under some circumstances, mobile node 107 migrates from its home network 103 to the remote network 105. This is illustrated by the dashed arrows in the figure. In one example, home network 103 is the enterprise network for an employer that owns node 107 and remote network 105 is a network of a hotel where the owner of node 107 visits.
In order for node 107 to have network conductivity at remote network 105, either it or network 105 must undergo some transformation. A process block 109 illustrates this transformation. As indicated, the static IP address of node 107 may be reconfigured or a network address translation component of remote network 105 must be reconfigured. As pointed out, both of these options fail to allow a convenient and easy connection.
In view of the above, it has become apparent to the inventors that hotels and other entities desiring to provide network connectivity for their visitors require an improved technique for providing that connectivity to the heterogeneous collection of visiting computers that they might encounter.